1. Field of Invention
The invention relates to a piston engine in which a piston reciprocates within a cylinder.
2. Description of Related Art
In recent years, Stirling engines, which are excellent in the theoretical heat efficiency, are drawing attention for the recovery of exhaust heat of an internal combustion engine mounted in a vehicle, such as a passenger car, a bus, a truck, etc., or of factory waste heat. Japanese Patent Application Publication No. 2005-106009 (JP-A-2005-106009) discloses a Stirling engine in which high pressure is maintained within a crankcase in order to obtain high output from the Stirling engine.
However, as for the Stirling engine disclosed in Japanese Patent Application Publication No. 2005-106009 (JP-A-2005-106009), no consideration is given to, for example, the pressure decline of the gas charged in the crankcase (casing) due to leakage of the gas.